Air filter



FIG. 1 is a front, right, and top perspective view of an air filter, showing my new design;

FIG. 2 is a rear, left, and bottom perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is a right side elevation view thereof;

FIG. 7 is a top plan view thereof;

FIG. 8 is a bottom plan view thereof; and,

FIG. 9 is another front, right, and top perspective view of the air filter of FIG. 1 in one state.

The broken lines depict portions of the air filter in which the design is embodied that form no part of the claimed design. 

CLAIM The ornamental design for an air filter, as shown and described. 